The invention relates to virtual storage systems, and more particularly, to configuring virtual storage mirrors in virtual hosts.
An important technology of storage systems is the mirror technology. The mirror technology of storage devices causes two storage devices mirrored with each other to store two copies of data, so that although only one virtual disk can be seen from a host side, a backend manages two virtual disks mirrored with each other which are the backups of each other, thereby increasing the availability and reliability of data storage. The drawback is that the necessary storage space is twice the actual available storage space, and it also has a higher cost. In general physical storage technology, a system manager can easily set which storage disks are mirrored with each other according to actual physical virtual disks.
Virtual storage collectively manages a plurality of storage devices (such as hard disk, RAID) in a certain manner, so that all the storage devices are commonly managed in one storage pool, and under a virtual host. Regardless of the background storage device, what is seen from the virtual host side is a logical mirror of its familiar storage device, which can be considered as a virtual disk label such as hard disk A, and hard disk B. The virtual host may process all the virtual storage devices, i.e., virtual disks, in the same manner with actual physical disk storages. Even if the physical storages vary, such logical mirrors will not vary, and the system manager does not need to worry about the background storages, but only needs to focus on managing the storage spaces. This technology makes the storage management operations, such as system upgrading, establishing and allocating virtual disks, changing RAID level, expanding storage space and so on, easier than before, so that the storage management becomes convenient and easy.
In the virtual storage, the mirror technology of a virtual storage is also included. Typically, the implementations of mirror technology of a virtual storage include two types: the mirror instructed by hardware structure and the mirror instructed by software structure. In the virtual storages of the mirrors instructed by the software structure, actual background physical storage devices may be very complicated, so the system manager usually uses an operating system on the virtual host or an interface provided by mirror dedicated software to instruct the mirrors, so that there is a mirror relationship between a plurality of virtual storage devices managed by the virtual host. Normally, the system manager enters a mirror command, and the operating system on the virtual host or the mirror dedicated software directly specifies the mirror relationship according to the sizes of the virtual storage device spaces. Since the virtual environment shields the correspondence between the virtual storage devices and the physical disks and the storage pools, there is a reliability problem in the mirrors specified by the mirror dedicated software.